Magnetic levitation support of running lengths



Nov. 23, 1965 R. s. DITTO 3,218,681

MAGNETIC LEVITATION SUPPORT OF RUNNING LENGTHS Filed March 21, 1962 3Sheets-Sheet 1 ls utl easuc (5 bMAFGSJEJIC FILAMENT- I I I I cunncm'FFORCE 12. MAGNET FIGZ INVENTOR.

RICHARD S. DITTO ATTORNEY N 1965 R. s. DlTTO 3,218,681

MAGNETIC LEVITATION SUPPORT OF RUNNING LENGTHS Filed March 21, 1962 3Sheets$heet 2 MOLTEN FILAMENT SOLIDIFIED FIUWEN T SOLIDIFIED FILAMENTFIG.5

IN VEN TOR. RICHARD S. DITTO BY WWg QWn -G ATTORNEY Nov. 23, 1965 R. s.DlTTO 3,213,681

MAGNETIC LEVITATION SUPPORT OF RUNNING LENGTHS Filed March 21, 1962 3Sheets-Sheet 3 MOLTEN FILAMENT TO SOURCE OF COIL POWER SOLIDIFIED FILAMENT FIG .6

INVENTOR.

RICHARD S. DITTO AT TO RNEY United States Patent 3,218,681 MAGNETICLEVITATION SUPPORT OF RUNNING LENGTHS Richard S. Ditto, Newark, Del.,assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., acorporation of Delaware Filed Mar. 21, 1962, Ser. No. 181,429 Claims.(Cl. 22--57.2)

This application is a continuation-impart of US. application S.N.102,090, filed April 10, 1961, now abandoned.

This invention relates to the magnetic levitation support of runninglengths of electrically conductive materials, and particularly to themagnetic levitation support of materials in travel having relatively lowinherent strength or cohesiveness, or which are subject to surfacemarring by contact with machinery or solid guides of any kind.

Magnetic levitation has heretofore been employed for the stationarysupport of conductive materials during the etiectuation of melting underthe influence of the same high frequency currents as are employed forthe levitation, as described in US. Patent 2,686,864. Relatively highamperage A.-C. currents are required for the purposes. The presentinvention is concerned with the magnetic levitation support of runningmaterials, such as metal rod and wire stock or other electricallyconductive forms, metal films or foils and the like, preferably with aminimum, or practically zero concomitant heating effect and withconstraint of the guided material to a precisely defined path, evenunder relatively high speeds of travel.

An object of this invention is the provision of a method and apparatusfor the support with or without concomitant guidance by magneticlevitation of running lengths of electrically conductive material. Otherobjects include the provision of a magnetic levitation guidance andsupport system which is low in first cost and in cost of operation,dependable in practice and adapted to a relatively wide variety ofindustrial uses, including the spinning of electrically conductivewires, filaments and fibers from molten metal, the conveyance of foilsand the like. The manner in which these and other objectives of thisinvention are attained will become clear from the detailed descriptionand the following drawings, in which:

FIG. 1 is a schematic representation of a preferred embodiment of thisinvention applied to metal spinning,

FIG. 2 is a diagrammatic representation of the magnetic field and forcerelationships applicable to a length of material being supportedaccording to this invention,

FIG. 3 is a perspective view of a preferred arrangement of solenoidsutilized for the support as well as horizontal constraint of a length ofmaterial in movement thereby,

FIG. 4 is a diagrammatic end representation of the apparatus shown inFIG. 3 looking in the direction of the spinneret and showing thedirections of current flow in both the solenoids and the filament,

FIG. 5 is a perspective view of a preferred arrangement similar to thatof FIG. 3, but utilizing permanent magnets instead of solenoids as thelevitation agency,

FIG. 6 is a side elevation view of one embodiment of shaped core whichcan be utilized to obtain a sloped path of filament travel, and

FIG. 7 is a perspective view of a solenoid pair provided with shapedcores of the configuration of FIG. 6, the path of filament travelobtained being drawn in.

Generally, this invention comprises a method and apparatus for thesupport and guidance of a running length of electrical conductor bymagnetic levitation comprising displacing the electrical conductor in agenerally predeter- 3,218,681 Patented Nov. 23, 1965 "ice mineddirection and passing an electric current through the conductor whilemoving the conductor through a magnetic field adapted to interact withthe field of the electric current passing through the conductor so as toconstrain the conductor in a predetermined path.

In the most common situation the magnetic levitation support provided bythis invention is proportioned so as to support substantially the weightof the electrical conductor against the force of gravity; however, theinvention is not so limited but can also provide a support force of amagnitude exceeding that of gravity, to thereby displace the conductor afinite amount upwardly in a vertical plane as hereinafter described withrespect to FIGS. 6 and 7.

Referring to FIG. 1, this invention is described in detail for the mostdiificult case, which is that in which the conductor in travel existsfirst in the molten state and thereafter cools to a solid which can thenbe handled conventionally. This is the situation for the spinning of ametal filament which is ejected in the molten state from a horizontallydisposed electrically conductive spinneret 14 provided in the bottom ofa furnace indicated generally at 9, which is heated by electricalresistance heater 10 mounted within thermal lagging 11. Ejection of themolten metal through spinneret 14 is facilitated by the application ofgas pressure to the melt through port 12 in the top of the furnace,which gas can be air or relatively inert gas, such as one of the noblegases (e.g., argon), or, in certain instances, nitrogen.

The extruded filament of molten metal is represented at 15 and is, ofcourse, so weak that it almost immediately breaks up into separate dropsunder the combined effects of the surface tension of the metal itselfand gravity, especially for such high density materials as the metals,unless support is provided. This support is afforded according to thisinvention as a combined support and guidance stage 18, followed by asupport stage solely at 19 after the metal has solidified. Finally, therelatively cool, hard, strong product filament is collected as a loosemass on a metal contact plate 20; however, it can be collected on a reelas readily, thereby dispensing with the contact plate or, in thealternative, utilizing the plate for temporary collection in conjunctionwith a following reel if desired.

In this instance, a D.-C. current is employed as the electric currentpassed through running filament 15, and this is furnished by aconventional source 21, which can be a 45 v. battery or the equivalent,provided with an adjusting rheostat 25, typically 400 ohms. Theelectrical circuit with the molten metal is made through conductor 26terminating in contact with electrically conductive spinneret 14. Thetraveling filament 15 is itself a good electrical conductor in both themolten and solid states, so long as its continuity is preserved, thuscompleting the electrical circuit through to metal contact plate 20, andthence to power source 21 through conductor 27.

Turning now to the magnetic levitation supports themselves, that ofsupport stage 19 is described first with reference to FIG. 2. This stageconsists of a pair of flat magnets 31 and 32 disposed with dissimilarpoles adjacent one another, with a gap 33 therebetween of typically /2".The magnetic flux field set up across the poles is represented at 34 forthe polarities shown and, from conventional electrical principles, ifthe current I passes through filament 15 to the right, as seen in FIG.2, a supportive force 36 is generated by interaction between themagnetic flux 35 surrounding the wire and field 34. It is desirable inthis instance that this force be just sufiicient to counterbalance theforce of gravity and any other downwardly acting forces, such asatmospheric down-drafts and the like, and this is readily accomplishedby regulating the flux density in the air gap 33 as well as the amountof current I passed through filament 15. Stage 19 as described isperfectly satisfactory for magnetic levitation support solely; however,it does permit some lateral drift between the magnet faces, which makesit desirable to use this construction only on relatively solid, coherentmaterial, such as materials already cooled past the completely moltenstage.

Stage 18, shown in FIGS. 3 and 4, is effective to provide combinedguidance and support and is, accordingly, preferred for use in regionswhere molten or near-molten materials are in transit. In this case theco-operating flux generators are two solenoids 40 and 41 disposed so asto define a V trough 42 of included angle through which strand 15passes. Typically, solenoids 40 and 41 can be 70 turn coils of copperfoil measuring 3" X 0.005" insulated with 5 mil thick polyethyleneterephthalate film, the whole being coated with varnish. In theapparatus employed for metal spinning as hereinafter described, the coilwas wrapped around a rectangular hollow wood core measuring 2" X 3" Xwithin which was placed a rectangular soft steel (SAE 1040) core of1.25" X 3" X 14.25" size. While iron-core coils are preferred, air-corecoils can also be used. Solenoids 40' and 41 are supplied with directcurrent through leads 43 and 44 (shown for solenoid 41 only in FIG. 3)connecting with a D.-C. power source 48, typically 24 amperes, 5 volts.With the direction of current flow indicated for the coil currents I andthe filament current I of FIG. 3, the directions of the magnetic fieldsgenerated in the vicinities of the solenoids and the filament are(looking in the direction of spinneret 14) as indicated in FIG. 4. Thisproduces an upwardly directed force which supports the filament againstthe effect of gravity and, at the same time, due to the inclinations ofthe solenoids from the vertical, there are produced balanced horizontalcomponents of force which constrain the filament to a quite precise pathin the horizontal plane, thus adding a guidance function to that oflevitation. An included angle 0 of 90 between the solenoids has provedsatisfactory; however, it will be understood that this can be modifiedwidely, depending upon the degree of guidance required and other designconsideration.

The magnitudes of the support forces employed in the practice of thisinvention are as follows for the two simplest cases involving D.-C.first and, thirdly, for the general case involving either AC. or DC.

Case I.H0riz0ntal D.C. magnetic field Referring to FIG. 2, the DC.current I consists of charges (electrons) Q moving with a velocity V.The magnetic flux density in the air gap of the magnets is B.

Accordingly, each charge moving in the magnetic field will experience anupwardly directed force F:QVB, or, over a representative element of theconductor, the force will be dL F Q B where Since the Coulomb forces ofattraction between the electrons and the positive ions of the conductorfar exceed the external force F, the latter is effectively applied tothe conductor. Differentiating,

4 where dQ m I whereupon dFzIBdL Thus, the total force developed on aconductor of length L in a uniform magnetic field is:

F=-IBdl which, on integration, gives F:BIL. This, in scalar notation, isF =BIL sin a, where a is the angle between B and L.

Since, for most applications, 0::90", and sin :1, the equation againresolves to F :BIL.

Case II.-N0n-horiz0ntal D.C. magnetic field This is the case where a DC.current carrying conductor is disposed in a magnetic field that is atright angles to the axis of the conductor, but the field is inclined atan angle y to the horizontal.

The FzBIL equation of Case I is completely applicable, except that themagnitudes of the two components F the vertical force, and P thehorizontal force, must be taken account of.

Thus,

F z-BlL cos y and F zBlL sin y Accordingly, the total force applied tothe conductor,

in complex notation, is:

F:F +F :BIL(sin y+j cos y) In the common case shown in FIG. 4, whereboth vertical and horizontal support is desired, the two solenoids 40and 41 are so disposed with respect to each other that the E, componentscancel so long as the filament conductor is located in the verticalcentral plane of the coil cross section. The vertical upward force F,,decreases as the conductor moves upward into regions of decreasing fluxdensity. As a result of these combined actions, both horizontal andvertical equilibrium positions are speedily established.

Case III.-General situation applicable to either D.-C. or A.-C..conductor current and magnetic field The following analysis assumes nofixed angular relationship between the current carrying conductor andthe magnetic field. Moreover, the current employed in the conductor andfor magnetic field generation can be either D.-C., A.-C. or anycombination of both, it being understood, however, that the same sourceis utilized for both the conductor and field circuits.

The final equation of Case I, F:BIL sin a, is applicable, where, for thegeneral case postulated, the individual terms constitute B:B cos wt 1:1COS(wt|-) where, w=angular frequency, t time, and =phase angle of Irelative to B, and the subscript m denotes maximum value.

Accordingly, for the general case.

F=(B cos wt) [1 cos (wt+)]L sin a This, generalized for the furthersituation Where the magnetic field is inclined at an angle y to thehorizontal, becomes:

F=F +F (B cos wt) [1 cos (wt +)]L sin a(sin y+j cos y) or, with termscollected,

F=BIL[cos wt cos (wt-H3) sin a] [sin y+j cos y] Inspection of this lastequation shows the complete feasibility of employing an alternatingfield in conjunction with an alternating current in the conductor,wherein both have the same frequency and zero phase angle. Under thesecircumstances the force components pulsate at a rate of 20). Theexistence of a phase angle results in negative force components as wellas positive ones and, at :l80, the forces become downwardly directed.Where D.-C. exclusively is employed, w= and =0, whereupon B and 1 becomedirect continuous quantitles and the equation reverts to the D.-C. CaseII form.

The embodiment of stage 13 shown in FIG. 5 utilizes permanent magnets 45and 46, with polarities as indicated, in V arrangement as a substitutefor the solenoids of FIGS. 3 and 4. The width, w, of such magnets cantypically be 1. Such permanent magnets are equally as effective assolenoids in the accomplishment of levitation; however, they, of course,possess the disadvantage of being non-regulable in their magneticaction. Nevertheless, in installations involving high temperatureservice, they are referred, since some ceramic magnets now availableoperate up to 600 C.

The operation of this invention is described in one example withreference to the horizontal spinning, using D.-C. with air cooling of alead metal filament. This metal was spun with the apparatus shown inFIG. 1, the temperature of the melt in furnace 9 being maintained atabout 340 C. and 10 lbs. air pressure being applied through port 12 toforce the molten metal out of spinneret 14. The bore of spinneret 14measured 0.005" and the metal filament finally recovered from contactplate 20 measured 0.0045 diameter.

The spacing between the outer face of spinneret 14 and the adjacent faceof stage 13 was about one foot, and stage 10 measured 15 long in thedirection of filament travel. The flux density of stage 18 having theconstruction hereinbefore described was 100 gauss.

Stage 10 was 2" long and disposed 24 from the adjacent face of stage 18and, in this instance, was of the design of FIG. 2, developing a fluxdensity of 1000 gauss. Finally, contact plate 20, measuring 8 x 8", wasdisposed with its center 9 from the adjacent face of stage 19, and 5feet from the outside face of spinneret 14-.

Using a current supply I of 75 ma. passed through the filament in thedirection from contact plate 20 towards spinneret 14, it was possible tospin filament at a rate of about 300 yds./min. with trajectorymaintained steadily on the line course drawn in FIG. 1. At the outset,the metal filament may break up so rapidly that it will not constitute acomplete electrical path. This difiiculty is overcome by providing amovable metal paddle connected to plate 20 by a flexible conductor, theoperator then being able to string up the filament by first bringing thepaddle into contact with the molten metal adjacent the spinneret andthen traversing it through the supportive magnetic fields in the line oftravel desired, whereupon support is provided by each device in turn asrepresented in FIG. 1. The vertical fall of the filament over the fulllength of its travel was 24 and the clearance above stage 19 was 2".From visual observation it was determined that the filament wasapparently solid by the time it left stage 18 in the direction of stage19, and that it clearly existed in the molten state for about 15 fromthe outside face of spinneret 14. In contrast, when the current suppliedto stage 18 was cut off, the molten stream broke into separate dropletswithin a distance of 12" from the spinneret, making it impossible toobtain a continuous filament product.

With steady currents applied to both solenoids and filament, and with nostrong air drafts or outside disturbance, the filament seeks anequilibrium position at a point in space wherein the upward forceapplied to the filament by interaction of the magnetic fields, justbalances the weight of the filament. Filament velocity has no ef feet onthe stability of support; however, more precise guidance is obtainedwhere there is laminar flow than turbulent flow. Thus, with laminarflow, the filament 6 wandering in a transverse direction with respect tothe solenoids of stage 18 is limited to about 4, Whereas, with turbulentflow, the filament wandering may be as much as :3.

The gage uniformity of the filament product obtained from the process ofthis invention is good, being about 10%. The variation in gage in thespecific metallic lead example reported was in large part due to theprogressive clogging of the spinneret orifice by lead oxide particlesthat were found to have contaminated the melt. The surface of thecollected lead filaments was bright, shiny and smooth. In test runsaveraging 3 to 4 minutes duration unbroken filament lengths of about1000 yards were easily obtained.

It will be understood that an 1 R heating effect is produced in filament15 by passage of current therethrough and this heating is a factor whichmust be taken into account in a process such as metal spinning.Actually, the balance of air cooling against levitation current isfavorable to the production of relatively large diameter wire stockusing conventional solenoid or permanent magnet levitating supports.However, with stock of larger diameter, the weight of the metal intransit can become so high that the filament current required inconjunction with the usual commercially available magnet and coilaccessories can be sufficient to generate enough heat in the filament tocounterbalance that lost to the surrounding cool air. Under theseconditions the metal remains molten and, thus, the spinning processbecomes inoperable. The various conditions applicable to each metal aredifferent and, of course, some metals can be spun in considerably largerdiameters than others. It will be understood that, in some instancesprotracted retention of metal in the form of a molten stream suspendedin contact with a gas can be desirable, as in conducting gas-metalreactions for metal purification or the like, and, accordingly, largeheating current throughputs to the metal are then a positiverequirement.

In another test, 60 cycle A.-C. was employed for both the conductor andthe field generator currents. No particular diificulty was encounteredin matching the phase angle of the solenoid power with that of thefilament and the product obtained was indistinguishable in quality fromthat produced with D.-C. For extremely fine fibers (i.e., those lessthan about 1 mil diameter), a A.-C. sets up a cyclic vibration in thefilament which is positively advantageous, in that it enhances the heatloss to the atmosphere.

It appears that the effective surface tension of molten metals can bedrastically altered in at least some cases by the presence of oxidelayers on the surface of the material, or by the presence of traceimpurities. Oxidation can be readily avoided by the use of inert gas asthe pressurized medium employed for forcing metal out of the spinneretand, of course, the entire apparatus of this invention can beconveniently housed within an inert atmosphere to safeguard againstlater-occurring oxidation.

A second apparatus was employed for yet other extrusions of continuousmetal filaments, using D.C. current, wherein solenoids 40 and ll ofcombined support and guidance stage 18 consisted of turns of copper foilmeasuring 3" wide x 0.005" thick, insulated with 0.001 thickpolyethylene terephthalate film and the whole coil assembly was coatedwith varnish. Each coil was wrapped around a hollow rectangular woodcore measuring 2" x 3 x 29", within which was inserted a rectagnularsoft steel (SAE 1040) core measuring 1.25 X 3" x 28.25. The extrusionswere made in air at nearstandard temperature conditions.

Stage 18 was spaced horizontally from spinneret 14 at various distanceswithin the range of about 12" to 15" during the different testshereinafter reported, the vertical drop from the spinneret to plate 20being maintained constant at 24". Stage 19 was omitted from theapparatus during these tests.

Material Extruded 50-50 Lead-Tin Alloy 6001* Aluminum SpinningTemperature, C 200 200 200 099 600 Spinnerct Orifice Diameter,

Inehes 0. 004 0. 007 0. 010 0. 006 0. 009 Extrudate Diameter, Inches. O.0035 0. 0062 0.0085 0. 005 0. 0070 Spinning Pressure, psi. 2O 20 20 40Filament Velocity, yds./min 270 220 330 800 900 Distance from spinneret14 to Contact Plate 20, in it 5 12 8 10 Filament Current I, amps 0. 0300. 100 0. 200 0. 025 0. 055 Solenoid Current, amps 45 45 45 25 FluxDensity of Stage 18, in

gauss H 220 220 220 130 130 *A.S.T.M. Metals Handbook 8th Edition (U.S.Government Spec. No. QQA-325) nominal analysis: Mg 1.00%, Si 0.6%, Cu0.25%, Cr 0.25%, balance Al.

In all of the tubulated spinning runs, continuous unbroken lengths ofproduct were easily obtainable, together with better than 10% gageuniformity and good surface quality.

The foregoing description has been devoted to the guidance andlevitation of a filament traveling in a straight projected path;however, this invention can be utilized to bend the course of thefilament in any way desired. Thus, by a given arrangement of magneticstages it is possible to cause the strand to take an undulatory courseof travel. Moreover, it the assembly of solenoids shown in FIGS. 3 and 4is turned about a horizontal axis to a new position lacking symmetrywith respect to the vertical plane, the filament will bend in agenerally horizontal plane and, in fact, can be made to make a sharp 90turn, the filament tending to turn towards that coil or magnet whichlies nearest to a horizontal position as compared with the other coil ormagnet. Also, filaments have been made to follow 360 loop patterns ingenerally vertical planes, and helical paths of travel are likewisereadily achieved.

A wide variety of magnetic field configurations adapted to obtainpredetermined paths of travel of the filaments or other materials can,of course, be provided. Thus, a field generator having a solenoid widthdecreasing linearly from a maximum dimension adjacent the spinneret to aminimum dimension at the product collection end is efiective to give adownwardly inclined path of filament travel. A convenient way ofachieving this is by simply utilizing shaped iron cores for thesolenoids, such as that shown in side elevation at 50 in FIG. 6. Herethe core has full width for about of its length on the end disposednearest the spinneret, after which it is decreased linearly at a slopeof about over 20% of its length to half width, and maintained at thisvalue for the remaining 40% of its over-all length. As shown in FIG. 7,a pair of solenoids 40 and 41' disposed in the same general relationshipas that detailed for FIG. 3, but provided with cores shaped as shown inFIG. 6, imparts a brief rise in the travel of filament 15' as indicatedat 1', followed by a smooth downward deflection in the region s,completed by horizontal travel over the balance of the course betweenthe solenoids. A filament angle in the region s of about 15 measuredabove the horizontal contributes a hydrostatic force component appliedto the molten metal which counteracts a tendency for the stream to breakup into droplets under the influence of surface tension.

It will be understood that a single pair of solenoids can be utilizedfor the support of a multiplicity of filaments in process, so long asmutual interference therebetween during travel is safeguarded against.This can be assured by spacing the spinneret holes a sufiicient distanceapart so that the filaments do not contact one another, at least notduring the critical molten state. It is also possible to employ a gradedsize of spinneret hole varying from a minimum diameter at the top to amaximum at the bottom, so that the spun filaments possess differentcharacteristics masses and therefore travel along individual paths.

Another design advantage is that the field generators can be fabricatedin unique cross sectional shapes which each possess characteristic fluxdistributions and thus enable the application of predeterminedsupportive or guidance forces at any point desired along the line oftravel, as well as the securing of a smooth variation in these forcesalong the entire line of transit.

While the foregoing description concerns molten-solid filament supportand guidance, obviously the same principles are completely applicable tothe handling of allsolid films, foils or the like, obtaining theadvantages of support and guidance without the necessity for physicallycontacting the metal in transit.

By way of distinguishing the forces applied to the electrical conductor,the force impelling the conductor through the magnetic field is referredto in the claims by the term displacing, and this, of course, can besupplied by a combination of gravity and the pushing action of theejected molten metal stream as in the metal spinning embodiment of thisinvention, or the running length can be pulled along by pinch rolls in aregion where the material is in the solid phase. Such forces are vectorquantities and are oriented in a predetermined direction. The forceswhich can be applied to the running length by the magnetic interactionare, as hereinbefore described, of an exceedingly great variety whichgenerate, either alone or as resultant with other magnetic interactions,gravity, surface tension and the like, support forces which constrainthe conductor to practically any predetermined path desired.

It Will be apparent that this invention can be modified extensivelywithin the skill of the art without departure from its essential spirit,and it is intended to be limited only by the scope of the followingclaims.

What is claimed is:

1. A method of spinning an electrically conductive filament comprisingejecting said filament in the molten state in a predetermined direction,passing an electric current from an extraneous source in electricalcircuit with said filament through said filament and maintaining amagnetic field adjacent to said filament, the field of said electriccurrent and said magnetic field having magnitudes and directionsdeveloping by interaction therebetween magnetic levitation support forsaid filament while said filament is solidifying as a result of heatloss to the surroundings.

2. A method of spinning an electrically conductive filament according toclaim 1 wherein said filament within which said electric current ispassed is directed along a path with respect to said magnetic fieldadjacent to said filament additionally developing opposed balancedhorizontal force components applied to said filament substantiallyconstraining said filament against sidewise movement in the course oftransit.

3. Apparatus for spinning an electrically conductive filament comprisingin combination a spinneret ejecting said filament in the molten state ina predetermined direction, means including a source of electric currentestablishing a completed electrical circuit through said filament andseparate means generating a magnetic field in proximity to said filamentof a magnitude and direction interacting with the magnetic fieldexisting about said filament as a result of flow of electric currentfrom said source therethrough and developing an upwardly directed forceconstraining said running length of said filament in a predeterminedpath while said filament is solidifying as a result of heat loss to thesurroundings.

4. An apparatus for the support of a running length of electricalconductor by magnetic levitation comprising in combination meansdisplacing said conductor in a generally predetermined direction, meansincluding an extraneous source of electric current establishing acompleted electrical circuit through said conductor and means generatinga magnetic field in proximity to said conductor of a magnitude anddirection with the interacting magnetic field existing about saidconductor as a result of ilow of electric current from said sourcetherethrough and developing an upwardly directed force on said conductorof a magnitude proportioned in extent in the direction 2,349,950 5/1944Forrnhals 18-8 of conductor travel constraining the path of travelthereof 2,586,046 2/ 1952 Huebner 2257.2 to a substantiallypredetermined shape in a vertical plane. 2,664,496 12/ 1953 Brace21910.51

5. An apparatus according to claim 4 wherein said 2,686,864 8/ 1954Wroughton 22-200.1 means generating said magnetic field comprise metalcore 5 2,879,566 3/ 1959 Pond 22200.1 solenoids wherein the metal coreof each of said solenoids is shaped with a side elevationalconfiguration generally FOREIGN PATENTS matching said predeterminedshape of said path of travel 1 258 180 2/1961 France of said electricalconductor.

References Cited by the Examiner 10 MARCUS U. LYONS, Primary Examiner.

UNITED STATES PATENTS WINSTON A. DOUGLAS, MICHAEL v. BRINDISI, 2,108,3612/1938 Asakawa 188 Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,218,681 November 23, 1965 Richard S. Ditto It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 4, line 68, for "P read F column 7, line 17, for "tubulated" readtabulated column 8, line 72, for "direction with the interacting" readdirection interacting with the Signed and sealed this 13th day ofDecember 1966.

( L) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner ofPatents

1. A METHOD OF SPINNING AN ELECTRICALLY CONDUCTIVE FILAMENT COMPRISINGEJECTING SAID FILAMENT IN THE MOLTEN STATE IN A PREDETERMINED DIRECTION,PASSING AN ELECTRIC CURRENT FROM AN EXTRANEOUS SOURCE IN ELECTRICALCIRCUIT WITH SAID FILAMENT THROUGH SAID FILAMENT AND MAINTAINING AMAGNETIC FIELD ADJACENT TO SAID FILAMENT, THE FILED OF SAID ELECTRICCURRENT AND SAID MAGNETIC FIELD HAVING MAGNITUDES AND DIRECTIONSDEVELOPING BY INTERACTION THEREBETWEEN MAGNETIC LEVIATION SUPPORT FORSAID FILAMENT WHILE SAID FILAMENT IS SOLIDIFYING AS A RESULT OF HEATLOSS TO THE SURROUNDINGS.